The present invention relates to a method and apparatus for producing spun yarn having a real twist.
For over a century, the ring traveller method has played a leading part in the art of producing spun yarns. With the recent increase in labor and energy costs, however, research and development efforts have been made to provide more efficient and innovative methods for producing spun yarns, in an attempt to replace the ring traveller method wherein operation involves low productivity and considerable electric power consumption on the order of 60 to 80% of the total power requirements for the entire spinning process.
Typical of such innovative methods is the one known as the rotor-type open end spinning method. This method permits more than three times as high a rate of production as does the ring-traveller method. As a more recent development, a method known as the fasciated yarn spinning method is now available. This method permits a still higher range of spinning velocities, on the order of 100 to 200 m/min. As far as rate of production is concerned, truly remarkable progress has been made in the last decade.
As regards end uses of spun yarns produced by these innovative processes, certain markets have been developed which can best utilize the characteristic features of these yarns. However, these yarns, in their present form, are not suitable for replacement of ring spun yarns. They are substantially different from ring spun yarns in yarn structure and properties, and unlike ring spun yarns, they lack general-purpose properties. Accordingly, their end uses are limited.
In order to further quantity-wise expansion and development in use of such innovative yarns, therefore, it is most important that there must be improvements well adapted for general-purpose uses, not to speak of the necessity of such high rate of production to be maintained as at present. To this end, it is necessary that they must have a structure similar to ring spun yarn, that is, a yarn structure having good fiber arrangement and evenly distributed twist. Indeed, a process which could permit production of a yarn having such a structure at an economically feasible rate and on a high volume basis would possibly replace the ring spinning method which involves rather inefficient operation.
In addition to the ring-traveller method, there is another established spinning method known as the tufted twisting method, which can produce spun yarns having real twist and relatively good fiber arrangement.
In this method a roller-drafted sheaf of staple fiber bundle is tufted by intermittent drafting. Tufts, which represent a small mass of staple fibers drawn out of said staple fiber bundle, so formed are sequentially superimposed on fiber ends being twisted by the rotation of a rotating spindle. In this manner a spun yarn having real twist is produced.
According to this technique, a spun yarn having a complete form of real twist can be obtained. However, there is a limitation that one turn is given for each turn of the rotating spindle. Therefore, if an economical spinning velocity is to be obtained, it is necessary to increase the rotational speed of the rotating spindle. The problem here is that if the spinning velocity is increased, fibers adjacent the rotating spindle may fly away under centrifugal force and the fiber arrangement may be disturbed. These adverse effects limit the spinning velocity. Therefore, in order to utilize this technique it is essential that the number of turns imparted by the rotation of the rotating spindle should be increased and that means should be provided to prevent any possible adverse effect of centrifugal force.